In the related art, there is a method that optimizes a layout design or a mask, using an assist pattern (sub-resolution assist feature (SRAF)), as one of the methods for improving a lithography margin of an exposure pattern (a design pattern which is a main pattern) in a semiconductor lithography technique.
As an SRAF arrangement method, there is a rule-based SRAF technique that arranges an SRAF in the vicinity of a design pattern according to an SRAF arrangement rule. In addition, there is a model-based SRAF technique that arranges an SRAF on a design pattern using a certain model.
However, in the rule-based SRAF technique, in some cases, it is difficult to ensure an appropriate lithography margin. In addition, SRAF arrangement that deviates from the SRAF arrangement rule in the rule-based SRAF technique is required. In this case, it is difficult to appropriately arrange the SRAF. In contrast, in the model-based SRAF technique, it takes a lot of time to calculate a coherence map representing the coherence of the design pattern. In addition, in the model-based SRAF technique, in some cases, it is difficult to derive an appropriate SRAF shape from the coherence map.
Therefore, it is preferable to easily arrange an SRAF on the design pattern, on which it is difficult to arrange the SRAF, in a short time.